Conductive composite film and preparation method and application thereof

Abstract

The invention discloses a conductive composite film and a preparation method and application thereof. The conductive composite film structurally comprises a transparent conductive network and a dielectric diffuse reflection layer, wherein the transparent conductive network is arranged on the surface of the dielectric diffuse reflection layer; wherein the medium diffuse reflection layer is formed by compounding a high-refractive-index material and a transparent elastic polymer material. The novel conductive composite film with high conductivity, high reflectivity, good mechanical stretchability and environmental tolerance is constructed by combining the transparent conductive network and the dielectric diffuse reflection layer, and the performance and stability of a photoelectric device can be remarkably improved by using the novel conductive composite film as the back electrode of the photoelectric device. The method is simple in process, low in energy consumption, low in cost and good in compatibility with a device process.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and in particular to a conductive composite thin film, its preparation method, and its application. Background Technology

[0002] Metal thin-film electrodes are currently the most widely used back electrodes. The most critical indicators for evaluating the performance of metal thin-film electrodes are conductivity and reflectivity. In addition, surface flatness is also an important indicator. Metal thin-film electrodes are generally prepared using vacuum evaporation deposition. The specific process is as follows: under vacuum conditions, the coating material is evaporated by heating and vaporization, and the particles fly to the substrate surface and condense to form a film. Vacuum evaporation deposition is an early and widely used vapor deposition technology. It has the advantages of simple film formation method and high film purity and density. However, it does not fully utilize raw materials, and the preparation cycle is long, ranging from several hours to tens of hours. Furthermore, this process relies on expensive large-scale vacuum evaporation deposition equipment, resulting in high energy consumption and high cost.

[0003] In recent years, researchers have proposed using conductive fillers such as conductive polymers, carbon nanotubes, graphene, printed metal meshes, and silver nanowires to prepare printed back electrodes. However, the performance of back electrodes prepared by most of these methods is difficult to match that of metal thin-film electrodes. For example, the conductive polymer poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) (PEDOT:PSS) typically has low conductivity and poor chemical stability and environmental weather resistance; most importantly, this electrode lacks reflectivity. Another example is the self-adhesive dry-printed electrode made from graphene, which, even after doping with gold and silver particles, still has a sheet resistance as high as approximately 750 Ω / sq, far exceeding that of metal thin-film electrodes, and its reflectivity is almost zero. Back electrodes prepared by spraying silver nanowire dispersions have proven to have the best conductivity among these methods, maintaining 100 Ω / sq while achieving 90% light transmittance, and also exhibiting a smooth surface, bend resistance, and good adhesion. However, this back electrode printing is a wet printing process, and the solvent of the dispersing material will cause some damage to the underlying material and structure. In addition, the back electrode still does not have a reflective function.

[0004] Therefore, developing low-cost and rapid methods to fabricate printed back electrodes with excellent electrical, optical, and mechanical properties has been a continuous goal of the industry. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a conductive composite thin film, its preparation method and application, to solve the technical problems of complex processes or high mechanical brittleness, insufficient reflectivity and poor compatibility with fully printed device processes caused by the reliance on vacuum conditions for the preparation of back electrode materials of flexible optoelectronic devices in the prior art.

[0006] In a first aspect, the present invention provides a conductive composite film, the structure of which includes: a transparent conductive network and a dielectric diffuse reflection layer, wherein the transparent conductive network is disposed on the surface of the dielectric diffuse reflection layer; wherein the dielectric diffuse reflection layer is composed of a high refractive index material and a transparent elastic polymer material.

[0007] Secondly, the present invention provides a method for preparing a conductive composite thin film, comprising the following steps: S1. A transparent conductive network is formed on the substrate surface; S2. The raw material of the dielectric diffuse reflection layer is coated onto the surface of the transparent conductive network, and after curing, a conductive composite film is obtained.

[0008] Thirdly, the present invention provides an application of a conductive composite film, which is applied to a back electrode.

[0009] Compared with the prior art, the beneficial effects of the present invention include: This invention combines a transparent conductive network with a dielectric diffuse reflection layer to construct a novel conductive composite film that possesses high conductivity, high reflectivity, good mechanical stretchability, and environmental resistance. Using this film as the back electrode of optoelectronic devices can improve device manufacturing efficiency and enhance the performance and stability of the devices. The process of this invention is simple, energy-efficient, low-cost, and highly compatible with device fabrication processes. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of one embodiment of the conductive composite thin film provided by the present invention; Figure 2 These are SEM and AFM images of the conductive composite film prepared in group 4 of Example 1 of this invention; wherein, (a) is a SEM image, (b) and (c) are AFM images; Figure 3 This is a resistance variation diagram of the conductive composite film prepared in group 4 of Example 1 of the present invention; wherein, (a) the relationship between tensile strain, number of cycles and sheet resistance, and (b) continuous bending cycle with a bending radius of 2 mm; Figure 4 This is a resistance change graph of the conductive composite film prepared in group 4 of Example 1 of the present invention; wherein, (a) 100 °C high temperature for 10 h, (b) air exposure for 30 days; Figure 5 These are the JV characteristic curves of the organic solar cells prepared in Examples 2-3 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0012] Please see Figure 1 In a first aspect, the present invention provides a conductive composite film, the structure of which includes: a transparent conductive network and a dielectric diffuse reflection layer, wherein the transparent conductive network is disposed on the surface of the dielectric diffuse reflection layer; wherein the dielectric diffuse reflection layer is composed of a high refractive index material and a transparent elastic polymer material.

[0013] This invention utilizes the high conductivity and high transmittance of a transparent conductive network, combined with a dielectric diffuse reflection layer, to create a conductive composite film that combines high conductivity and high reflectivity for the first time. The conductive composite film of this invention consists of two parts: first, a transparent conductive network, which serves as the conductive layer and has micron-sized pores, exhibiting high transparency to visible light, thus enabling the dielectric diffuse reflection layer to perform its reflective function; second, a dielectric diffuse reflection layer, which serves as a high-reflectivity optical layer, utilizing a high-refractive-index material to achieve diffuse reflection of light, thereby improving light utilization and the photoelectric conversion efficiency of the device. This invention achieves functional decoupling of the conductive and reflective layers by forming a composite structure of the transparent conductive network and the dielectric diffuse reflection layer. This composite structure not only maintains high surface conductivity but also achieves high optical reflectivity through the dielectric diffuse reflection layer, while simultaneously enabling the stretchability of the electrodes.

[0014] In this embodiment, the transparent conductive network is partially embedded in the surface of the dielectric diffuse reflection layer. "Partially embedded" means that the entire transparent conductive network is uniformly embedded in the surface of the dielectric diffuse reflection layer and has an exposed conductive surface.

[0015] In this embodiment, the transparent conductive network has high transparency in the visible-near infrared region, which is used to realize charge transfer between it and the material it contacts.

[0016] In this embodiment, the transparent conductive network is an AgNWs (silver nanowires) translucent conductive network. Due to its high aspect ratio and good conductivity, AgNWs can form a highly efficient translucent conductive network.

[0017] Furthermore, AgNWs have an aspect ratio greater than 1000, an average length of 20–50 µm, and an average diameter of 10–50 nm.

[0018] In this embodiment, the loading of AgNWs in the conductive composite film is 24~80 μg / cm³. 2 Optimal conductivity and light transmittance are achieved by controlling the loading of AgNWs within the above range.

[0019] In this embodiment, the high refractive index material is BaSO4 (barium sulfate) nanoparticles.

[0020] Furthermore, the particle size distribution of BaSO4 nanoparticles is 200~500 nm.

[0021] In this embodiment, the transparent elastic polymer material is polydimethylsiloxane (PDMS).

[0022] In this embodiment, the mass fraction of high refractive index material in the dielectric diffuse reflection layer is 40%~60%, and more specifically 50%. If the proportion of high refractive index material is too low, the reflectivity of the conductive composite film will be insufficient; if the proportion of high refractive index material is too high, the modulus of the conductive composite film will be too large, making it unable to adhere well to the device surface.

[0023] In this embodiment, the thickness of the dielectric diffuse reflection layer is 300~500μm. If the thickness of the dielectric diffuse reflection layer is too low, the reflectivity will decrease; if the thickness of the dielectric diffuse reflection layer is too high, the film rigidity will be too high, resulting in insufficient bonding effect.

[0024] In this embodiment, the diffuse reflective layer is a composite layer of a high refractive index material and a transparent elastic polymer material.

[0025] In this embodiment, the dielectric diffuse reflection layer includes a transparent elastic polymer material layer and a composite layer of high refractive index material and transparent elastic polymer material stacked together, and a transparent conductive network is disposed on the surface of the transparent elastic polymer material layer.

[0026] By employing the above-described dielectric diffuse reflection layer, this invention can significantly improve the adhesion of the overall structure. At the same time, since the transparent elastic polymer material has high light transmittance, it will not reduce the reflectivity of the overall device, and since the transparent conductive network remains unchanged, it will not affect the conductivity.

[0027] Secondly, the present invention provides a method for preparing a conductive composite thin film, comprising the following steps: S1. A transparent conductive network is formed on the substrate surface; S2. The raw material of the dielectric diffuse reflection layer is coated onto the surface of the transparent conductive network, and after curing, a conductive composite film is obtained.

[0028] In this embodiment, the substrate is at least one of glass, silicon wafer, aluminum foil, polyethylene terephthalate, polyethylene naphthalate, and polyimide.

[0029] In this embodiment, the transparent conductive network is an AgNWs ultra-transparent conductive network, and step S1 includes: S11, Provide AgNWs dispersion; S12. The AgNWs dispersion is coated onto the substrate surface and cured to obtain a transparent conductive network.

[0030] Further, step S11 includes: S111. Prepare an ethanol solution of silver nitrate (AgNO3), an ethanol solution of sodium bromide (NaBr), an ethanol solution of sodium chloride (NaCl), and an ethylene glycol solution of polyvinylpyrrolidone (PVP). S112. Mix the ethylene glycol solution of polyvinylpyrrolidone, the ethanol solution of NaBr, and the ethanol solution of NaCl evenly, then add the ethanol solution of AgNO3, and then let the reaction stand. After the reaction is completed, quench the solution in an ice-water bath to obtain the AgNWs reaction solution. S113. Mix the AgNWs reaction solution with ethanol, then add acetone to precipitate, remove the supernatant and disperse it in ethanol again. Repeat 2-3 times to obtain the AgNWs dispersion.

[0031] In step S111, the concentration of the silver nitrate ethanol solution is 20-30 g / L; the concentration of the sodium bromide ethanol solution is 0.3-0.5 g / L; the concentration of the sodium chloride ethanol solution is 0.4-0.6 g / L; and the concentration of the polyvinylpyrrolidone glycol solution is 10-30 g / L.

[0032] In step S112, the mass ratio of silver nitrate to sodium bromide, sodium chloride, and polyvinylpyrrolidone is 1:(0.001~0.005):(0.001~0.005):(1~1.2).

[0033] In step S112, the ethylene glycol solution of PVP, the ethanol solution of NaBr, and the ethanol solution of NaCl are mixed evenly by stirring at a speed of 200-400 rpm for 10-30 min.

[0034] In step S112, during the addition of the ethanol solution of AgNO3, the feeding temperature is 150~170°C, the feeding time is 30~50 min, and the feeding process is carried out under stirring conditions.

[0035] In step S112, the temperature of the static reaction is 150~170°C, and the static reaction time is 1~12h, preferably 2~3h.

[0036] In step S113, the volume ratio of AgNWs reaction solution to ethanol and acetone is 1:(0.5~1.5):(1~2).

[0037] Furthermore, in step S12, the concentration of the AgNWs dispersion is 0.5~2 mg / mL.

[0038] Furthermore, in step S12, a low-temperature water mist welding method is used for curing, and step S12 includes: coating the AgNWs dispersion onto the substrate surface, then spraying with water mist, and heating to evaporate the water to obtain a transparent conductive network. In this process, the capillary force between the AgNWs nodes and between the AgNWs and the substrate is used to achieve node welding, reduce the contact resistance at the nodes, and form a stable AgNWs transparent conductive network.

[0039] The curing temperature is 70~100°C, and the curing time is 1~10 minutes.

[0040] In this embodiment, step S2 includes: S21A. Mix high refractive index material and transparent elastic polymer material evenly to obtain composite colloid; S22A: The composite colloid is coated onto the surface of a transparent conductive network, and after curing, a composite of the substrate and the conductive composite film is obtained; S23A. The composite of the substrate and the conductive composite film is cooled to below the glass transition temperature of the transparent elastic polymer material, and the substrate and the conductive composite film are separated to obtain the conductive composite film.

[0041] This invention cools the composite of the substrate and the conductive composite film to below the glass transition temperature of the transparent elastic polymer material, thereby achieving higher elastic modulus and dimensional shrinkage in a frozen state. This results in higher stress being applied to the conductive composite film during the peeling process, enabling complete transfer of the conductive composite film and making the electrode surface smoother and more conductive.

[0042] Among them, the high refractive index material is ground before use to reduce the agglomeration between particles and improve the dispersion of nanoparticles in the matrix.

[0043] The curing temperature is 70~100°C, and the curing time is 1~3 hours.

[0044] In this method, the composite of the substrate and the conductive composite film is cooled to below the glass transition temperature by liquid nitrogen cooling.

[0045] In this embodiment, step S2 includes: S21B. Mix high refractive index material and transparent elastic polymer material evenly to obtain composite colloid; S22B: A transparent elastic polymer material and a composite colloid are sequentially coated onto the surface of a transparent conductive network, and after curing, a composite of a substrate and a conductive composite film is obtained. S23B: Cool the composite of the substrate and the conductive composite film to below the glass transition temperature of the transparent elastic polymer material, and separate the substrate from the conductive composite film to obtain the conductive composite film.

[0046] Among them, the high refractive index material is ground before use to reduce the agglomeration between particles and improve the dispersion of nanoparticles in the matrix.

[0047] The curing temperature is 70~100°C, and the curing time is 1~3 hours.

[0048] In this method, the composite of the substrate and the conductive composite film is cooled to below the glass transition temperature by liquid nitrogen cooling.

[0049] Thirdly, the present invention provides an application of a conductive composite film, which is applied to a back electrode.

[0050] This invention combines a transparent conductive network with a dielectric diffuse reflective layer to form a conductive composite film. When applied to the back electrode, it not only has high conductivity and high reflectivity, but also good mechanical stretchability and environmental resistance, which can significantly improve the performance and stability of flexible optoelectronic devices.

[0051] Furthermore, this conductive composite film can be used as a back electrode, or it can be composited with other back electrode materials, such as ITO and PEDOT:PSS films, to serve as a back electrode. The inventors have discovered that combining the conductive composite film of this application with a PEDOT:PSS film can leverage their synergistic effect, significantly improving the photoelectric performance of optoelectronic devices to a level comparable to metal thin-film electrodes.

[0052] Furthermore, the back electrode is mainly used in flexible optoelectronic devices, such as organic solar cells, flexible photodetectors, and flexible display devices.

[0053] Furthermore, conductive composite films are applied as back electrodes for optoelectronic devices using a dry bonding (solvent-free bonding) method. This dry bonding process avoids the corrosion of the active layer of the optoelectronic device by solvents, as is common in traditional wet bonding processes, thus improving the stability and reliability of the device.

[0054] Example 1 Example 1 provides a method for preparing a conductive composite thin film, comprising the following steps: (1) Preparation of AgNWs super-permeable conductive network Ethylene glycol (EG) was preheated to 170 °C. Ethanol solutions of AgNO3 (25.5 g / L), NaBr (0.412 g / L), and NaCl (0.464 g / L) were prepared. 550 mg of PVP (molecular weight 1.3 million) was weighed and dissolved in 25 mL of EG. The solution was placed in a 100 mL flask and then placed in an oil bath at 160 °C. The flask was magnetically stirred at 320 rpm to ensure complete dissolution and the formation of a homogeneous precursor solution. 2.5 mL of NaBr and 4 mL of NaCl were added to the precursor solution, and stirring was continued for 20 min. 20 mL of AgNO3 ethanol solution was continuously injected into the reaction system at a constant rate of 0.5 mL / min using a syringe pump. The reaction system temperature was maintained at 160 °C throughout the injection process to ensure the stability of the reaction conditions. Once the AgNO3 solution injection was complete, stirring was stopped, and the solution was stirred at 160 °C. The reaction was continued at °C for 2.5 h, and then the flask was quickly transferred to an ice-water bath for quenching to terminate the reaction, yielding an AgNWs reaction solution. 5 mL of the AgNWs reaction solution was mixed with 5 mL of anhydrous ethanol, and then 8 mL of acetone was slowly added dropwise. The mixture was allowed to stand until the aggregated AgNWs settled to the bottom of the container, and the supernatant was removed. The aggregated AgNWs were then redispersed in anhydrous ethanol, and the above operation was repeated three times to obtain an AgNWs dispersion with a concentration of 1 mg / mL.

[0055] The AgNWs dispersion was uniformly coated onto the silicon wafer surface using a spraying process, with the AgNWs loading controlled at 24 μg / cm³. 2 40μg / cm 2 64μg / cm 2 80μg / cm 2 The coated silicon wafer is placed on a heating stage at 80 °C. A humidifier is used to spray water mist onto the AgNWs electrodes for 10 seconds. The water is then evaporated under gentle heating at 80 °C. The nodes are welded by the capillary force between the AgNWs nodes and the substrate, reducing the contact resistance at the nodes and forming a stable AgNWs ultra-transparent conductive network film.

[0056] (2) Preparation of the dielectric diffuse reflection layer BaSO4 powder with a particle size of approximately 400 nm was ground in an agate mortar; PDMS prepolymer and curing agent (Dow Corning Sylgard 184) were mixed at a volume ratio of 20:1 to obtain a PDMS precursor solution; BaSO4 was uniformly dispersed into the PDMS precursor solution by mechanical stirring to obtain a composite colloid with a BaSO4 mass fraction of 50 wt.%; the composite colloid was uniformly coated onto an AgNWs transparent conductive network film; the coated substrate was placed in an oven at 80 °C for 1.5 h to cure, forming a dielectric diffuse reflection layer with a thickness of approximately 400 µm and high reflectivity and good mechanical properties on the surface of the AgNWs ultra-transparent conductive network film (the whole is a composite of the substrate and the conductive composite film).

[0057] (3) Peeling of conductive composite film The composite of the substrate and the conductive composite film was immersed in liquid nitrogen (-170 °C) for 10 s. Utilizing the glass transition behavior of PDMS elastomer, it achieved higher elastic modulus and dimensional shrinkage under frozen conditions, thereby applying higher stress to AgNWs during the peeling process and achieving complete transfer of AgNWs, ultimately preparing the AgNWs@PDMS / BaSO4 conductive composite film. Since the conductive composite film is generally adhesive, release paper was wrapped around its PDMS@BaSO4 side for easy subsequent use.

[0058] Example 2 Example 2 provides a method for preparing an organic solar cell, comprising the following steps: 1. Preparation of the PEI-Zn electron transport layer: 0.07 g of zinc acetate dihydrate was dissolved in 1 mL of a pre-prepared 0.5 wt.% PEIE (ethoxylated polyethyleneimine) solution to obtain a PEI (polyethyleneimine)-Zn precursor solution. 30 μL of the PEI-Zn precursor solution was spin-coated onto an ultrasonically cleaned ITO glass at 3500 rpm for 40 s, followed by annealing at 150 °C for 10 min to obtain a PEI-Zn film with a thickness of approximately 30 nm.

[0059] 2. Preparation of the active layer: Under a nitrogen glove box environment, pre-prepared active layer solutions of PM6:BTP-eC9:PC71BM and PM6:L8-BO were sequentially spin-coated onto a PEI-Zn film. The spin-coating speeds for PM6:BTP-eC9:PC71BM and PM6:L8-BO were set to 1500 rpm and 3000 rpm, respectively, with a spin-coating time of 40 s for both. After spin-coating, the PM6:BTP-eC9:PC71BM active layer solution required annealing at 100 °C for 10 min, while PM6:L8-BO did not require annealing. The thickness of both active layers was approximately 100 nm. The preparation methods for the active layer solutions are as follows: (1) PM6:BTP-eC9:PC71BM (poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2 [-ethylhexyl)carbonyl]thieno[3,4-b]thienodiyl]]:2,2'-((12,13-bis(2-butyloctyl)-12,13-dihydro-3,9-dinonylbisthieno(2”,3”:4',5')thieno(2',3':4,5)pyrrolo(3,2-e:2',3'-g)(2,1,3)benzothiadiazole-2,10-diyl)bis(methylene(5,6-chloro-3-oxo-1H-indene-2,1(3H)-diylidene)))bis(malononitrile):(6,6)-phenyl-C71-butyrate) Preparation of active layer solution: Weigh 9.0 mg PM6, 9.0 mg BTP-eC9 and 1.8 mg PC71BM, dissolve in 1 mL chlorobenzene, and then add 5 μL of additive 1,8-diiodooctane (DIO) is sealed and placed in a nitrogen glove box. It can be used after stirring at 50 °C for 12 h.

[0060] (2) Preparation of PM6:L8-BO active layer solution: Weigh 7 mg PM6 and 8.4 mg L8-BO, dissolve them in 1 mL chloroform, add 3 μL of additive DIO, seal and place in a nitrogen glove box, stir at 45 ℃ for 4 h before use.

[0061] 3. Preparation of PEDOT:F (fluorine-doped poly(3,4-ethylenedioxythiophene)) film: First, 2 mL of perfluorosulfonic acid polymer (PFSA) was mixed with 8 mL of deionized water, and 0.031 g of 3,4-ethylenedioxythiophene (EDOT) was added. The mixture was stirred at 1500 rpm for 30 min at room temperature to form a milky white emulsion. Then, 0.0615 g of FeCl3 was dissolved in 3 mL of deionized water and ultrasonically dispersed for 5 min. This solution was added dropwise (500 μL / time, 5 min interval) to the emulsion. The solution gradually changed from milky white to dark blue, indicating that the oxidative polymerization of EDOT was complete. After stirring overnight for 14 h, the mixture was centrifuged at 10500 rpm to achieve solid-liquid separation. The mixture was washed with deionized water to remove surface residues, and then dialyzed through a 500 Da semi-permeable membrane to remove unreacted EDOT monomers and oxidants. The purified product was centrifuged to obtain a blue-black solid. The solid was dispersed in an ethanol solution at a solid-liquid ratio of 5 mg / mL, and PFSA was added to achieve a concentration of 10 mg / mL. The solution was then sonicated using a cell disruptor for 6 h to obtain an ethanol dispersion of PEDOT:F. 30 μL of the ethanol dispersion of PEDOT:F was dynamically spin-coated at 3000 rpm for 40 s, followed by annealing at 100 °C for 3 min to obtain a PEDOT:F film.

[0062] 4. Preparation of PEDOT:PSS film: Ethylene glycol was added to PEDOT:PSS (PH1000) and stirred for 8 h to obtain an ethylene glycol solution of PEDOT:PSS (ethylene glycol mass fraction of 5 wt.%). PDMS prepolymer and curing agent were weighed and mixed at a mass ratio of 10:1. After removing air bubbles by vacuuming, the mixture was cured in an oven at 80 °C for 1.5 h to obtain a PDMS substrate. The ethylene glycol solution of PH1000 was spin-coated onto the plasma-treated PDMS substrate at a speed of 1000 rpm for 20 s, and then dried at room temperature for 2 min. The PEDOT:PSS on the PDMS substrate was then attached to the surface of the PEDOT:F layer, and the PDMS substrate was subsequently peeled off to obtain a PEDOT:PSS film with a thickness of 120 nm.

[0063] 5. Lamination of AgNWs@PDMS / BaSO4 conductive composite film: The AgNWs@PDMS / BaSO4 conductive composite film prepared in group 4 of Example 1 is cut to size (0.04 cm²) according to the device area. 2Afterward, in a glove box, accurately adhere it to the surface of the PEDOT:PSS (PH1000) film, gently pressing for 10 seconds to ensure a tight bond between the AgNWs@PDMS / BaSO4 conductive composite film and the PEDOT:PSS layer. Then, peel off the release paper on the back of the conductive composite film to complete device fabrication. During the bonding process, care must be taken to avoid introducing air bubbles and impurities to ensure device performance.

[0064] Example 3 Compared with Example 2, the only difference is that Example 3 uses only the AgNWs@PDMS / BaSO4 conductive composite film prepared in Group 4 of Example 1 as the back electrode (i.e., without the PEDOT:PSS film preparation step).

[0065] Comparative Example 1 Compared with Example 2, the only difference is that Comparative Example 1 uses vapor-deposited back electrodes, and the specific steps are as follows: After the PEDOT:F thin film was prepared, the sample was transferred to a vacuum evaporation machine and placed inside a fixed-shape mask. The effective area of ​​the device obtained through the mask was 0.04 cm². 2 When the vacuum level decreases to 1×10 −6 After Torr, a 70 nm thick Ag layer is deposited as the back electrode, thus completing the device fabrication.

[0066] Comparative Example 2 Compared with Example 2, the only difference is that Comparative Example 2 only uses a PEDOT:PSS layer as the back electrode, without the subsequent bonding step of AgNWs@PDMS / BaSO4 conductive composite film.

[0067] Performance testing (1) Surface morphology of AgNWs@PDMS / BaSO4 conductive composite film: Please see Figure 2 ,pass Figure 2 (a) It can be seen that in the conductive composite film prepared in Example 1, Group 4, AgNWs are distributed on the surface of the PDMS / BaSO4 dielectric diffuse reflection layer, and the AgNWs synthesized by the polyol method have an aspect ratio greater than 1000, an average length of 32.6 ± 8.9 µm, and an average diameter of 29.1 ± 2.9 nm. Figure 2 (b) It can be seen that the root mean square roughness (RMS) of the film surface is 6.1 nm, indicating that the coverage and filling of the AgNWs stacked network by the PDMS / BaSO4 dielectric diffuse reflection layer significantly reduces the surface roughness. Figure 2 (c) The height profile curve shows that although there is a certain difference in stacking height of AgNWs, the uniform wetting and filling of PDMS makes the overall surface tend to be flat.

[0068] (2) Photoelectric properties of AgNWs@PDMS / BaSO4 conductive composite film: The mass fraction of BaSO4 in the AgNWs@PDMS / BaSO4 conductive composite film was fixed at 50 wt.%, and the thickness of the diffuse reflective dielectric layer was 400 µm. To investigate the effect of the AgNWs network on the optical properties of the film, the AgNWs loading was adjusted to 80 μg / cm³ by controlling the AgNWs spraying volume. 2 64μg / cm 2 40μg / cm 2 24μg / cm 2 The sheet resistances Rs of the thin films were measured using a four-probe device, which were approximately 20, 25, 40 and 60 Ω / sq, respectively. Their reflectivity in the visible light band was also measured, and the photoelectric properties of the conductive composite films prepared based on different AgNWs loadings were recorded. The test results are shown in Table 1.

[0069] Table 1

[0070] Please refer to Table 1. As can be seen from Table 1, by adjusting the AgNWs density (i.e., loading amount), the present invention can controllably adjust the AgNWs@PDMS / BaSO4 conductive composite film in terms of low sheet resistance (20~60 Ω / sq) and high reflectivity (80%~90%). Furthermore, in group 4 of Example 1, the AgNWs loading amount is 80 μg / cm³. 2 At this time, the sheet resistance of the thin film is only 20Ω / sq, which is conducive to achieving optimal conductivity and reflectivity of over 80%.

[0071] (3) Mechanical properties of AgNWs@PDMS / BaSO4 conductive composite film: Please see Figure 3 ,pass Figure 3 It can be seen that the AgNWs@PDMS / BaSO4 conductive composite film maintains stable resistance within 20% cyclic tensile strain, and the resistance change rate is less than 10% after 1000 bending cycles (bending radius 2 mm). The shear strength of the electrode reaches 6.86 N, and its strong interfacial adhesion is verified by 3M tape peel test.

[0072] (4) Environmental stability of AgNWs@PDMS / BaSO4 conductive composite film: Please see Figure 4 ,pass Figure 4It can be seen that the AgNWs@PDMS / BaSO4 conductive composite film exhibits a resistance change rate of less than 10% after being placed at 100℃ for 10 hours; and a resistance change rate of less than 10% after being exposed to air for 30 days, demonstrating significant environmental tolerance.

[0073] (5) Photoelectric properties of organic solar cells: Please see Figure 5 ,pass Figure 5 As can be seen, when the AgNWs@PDMS / BaSO4 conductive composite thin film (group 4 in Example 1, with a reflectivity of approximately 82% and a sheet resistance of approximately 20 Ω / sq) is integrated onto an organic solar cell with a device structure of ITO / PEI-Zn / PM6:BTP-eC9:PC71BM / PM6:L8-BO / PEDOT:F / PEDOT:PSS / AgNWs@PDMS / BaSO4, the short-circuit current density (JSC) of the device is 24.67 mA / cm². 2 The photoelectric conversion efficiency (PCE) is 13.67%, which is close to the performance of the comparative device based on vapor-deposited silver electrodes (JSC = 23.72 mA / cm²). 2 (PCE = 14.87%). Device fabricated with a transparent conductive polymer PEDOT:PSS back electrode (JSC = 19.99 mA / cm). 2 Compared to the previous method (PCE = 10.31%), the dielectric diffuse reflection structure of the conductive composite thin-film electrode of this invention significantly improves the short-circuit current density of the device, thereby increasing the device efficiency by 3.36%. Furthermore, through... Figure 5 It can also be seen that, compared with devices fabricated using PEDOT:PSS alone as the back electrode and devices fabricated using AgNWs@PDMS / BaSO4 alone as the back electrode (JSC = 12.5 mA / cm²), the performance of PEDOT:PSS alone as the back electrode is significantly better than that of devices fabricated using AgNWs@PDMS / BaSO4 alone as the back electrode (JSC = 12.5 mA / cm²). 2 Compared to the previous method (PCE = 5.64%), this invention, by using a composite of PEDOT:PSS and AgNWs@PDMS / BaSO4 as the back electrode, can leverage the synergistic effect of the two and significantly improve device efficiency.

[0074] Compared with the prior art, the beneficial effects of the present invention include: Performance enhancement: The AgNWs@PDMS / BaSO4 conductive composite film achieves controllable adjustment of low sheet resistance (20~60 Ω / sq) and high reflectivity (80%~90%), significantly improving the photoelectric conversion efficiency of flexible optoelectronic devices.

[0075] Mechanical stability: The AgNWs@PDMS / BaSO4 conductive composite film exhibits excellent mechanical adaptability, maintaining stable resistance within 20% cyclic tensile strain, and a resistance change rate of less than 10% after 1000 bending cycles (bending radius 2 mm), meeting the dynamic deformation requirements of flexible and stretchable devices.

[0076] Environmental tolerance: The AgNWs@PDMS / BaSO4 conductive composite film exhibits a performance degradation rate of less than 10% after 10 h at 100 °C and 30 days of air exposure, demonstrating significant environmental tolerance and improving the long-term stability of the device.

[0077] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A conductive composite thin film, characterized in that, The conductive composite film comprises: a transparent conductive network and a dielectric diffuse reflection layer, wherein the transparent conductive network is disposed on the surface of the dielectric diffuse reflection layer; wherein... The diffuse reflective layer is composed of a high refractive index material and a transparent elastic polymer material.

2. The conductive composite film according to claim 1, characterized in that, The transparent conductive network is partially embedded in the surface of the dielectric diffuse reflection layer; and / or The transparent conductive network is an AgNWs ultra-transparent transparent conductive network; and / or... The AgNWs loading in the conductive composite film is 24~80 μg / cm³. 2 ; and / or, The high refractive index material is BaSO4 nanoparticles; and / or, The transparent elastic polymer material is polydimethylsiloxane; and / or, In the diffuse reflection layer, the mass fraction of the high refractive index material is 40%~60%; and / or, The thickness of the diffuse reflective layer is 300~500μm.

3. The conductive composite film according to claim 1, characterized in that, The diffuse reflection layer is a composite layer of a high refractive index material and a transparent elastic polymer material; or... The diffuse reflection layer comprises a transparent elastic polymer material layer and a composite layer of high refractive index material and transparent elastic polymer material stacked together, and the transparent conductive network is disposed on the surface of the transparent elastic polymer material layer.

4. A method for preparing a conductive composite thin film as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1. A transparent conductive network is formed on the substrate surface; S2. The raw material of the dielectric diffuse reflection layer is coated onto the surface of the transparent conductive network, and after curing, a conductive composite film is obtained.

5. The method for preparing the conductive composite thin film according to claim 4, characterized in that, The transparent conductive network is an AgNWs ultra-transparent conductive network, and step S1 includes: S11, Provide AgNWs dispersion; S12. The AgNWs dispersion is coated onto the substrate surface and cured to obtain a transparent conductive network.

6. The method for preparing the conductive composite thin film according to claim 5, characterized in that, Step S11 includes: S111, Prepare an ethanol solution of silver nitrate, an ethanol solution of sodium bromide, an ethanol solution of sodium chloride, and an ethylene glycol solution of polyvinylpyrrolidone; S112. Mix the ethylene glycol solution of polyvinylpyrrolidone, the ethanol solution of sodium bromide, and the ethanol solution of sodium chloride evenly, then add the ethanol solution of silver nitrate, and then allow the reaction to stand. After the reaction is completed, quench the mixture in an ice-water bath to obtain the AgNWs reaction solution. S113. Mix the AgNWs reaction solution with ethanol, then add acetone to precipitate, remove the supernatant, and then disperse it in ethanol again. Repeat this process 2-3 times to obtain an AgNWs dispersion; wherein... In step S111, the concentration of the silver nitrate ethanol solution is 20-30 g / L; the concentration of the sodium bromide ethanol solution is 0.3-0.5 g / L; the concentration of the sodium chloride ethanol solution is 0.4-0.6 g / L; the concentration of the polyvinylpyrrolidone glycol solution is 10-30 g / L; and / or, In step S112, the mass ratio of silver nitrate to sodium bromide, sodium chloride, and polyvinylpyrrolidone is 1:(0.001~0.005):(0.001~0.005):(1~1.2); and / or, In step S112, the ethylene glycol solution of polyvinylpyrrolidone, the ethanol solution of sodium bromide, and the ethanol solution of sodium chloride are mixed evenly by stirring at a speed of 200-400 rpm for 10-30 minutes; and / or, In step S112, during the addition of the silver nitrate ethanol solution, the addition temperature is 150~170°C, the addition time is 30~50 min, and the addition process is carried out under stirring conditions; and / or, In step S112, the temperature of the static reaction is 150~170°C, and the time of the static reaction is 1~12 hours; and / or, In step S113, the volume ratio of the AgNWs reaction solution to ethanol and acetone is 1:(0.5~1.5):(1~2).

7. The method for preparing the conductive composite thin film according to claim 5, characterized in that, In step S12, the concentration of the AgNWs dispersion is 0.5~2 mg / mL; and / or, The curing process employs a low-temperature water mist welding method, and step S12 includes: coating the AgNWs dispersion onto the substrate surface followed by water mist spraying, and heating to evaporate the moisture, thereby obtaining a transparent conductive network; and / or, The curing temperature is 70~100°C, and the curing time is 1~10 minutes.

8. The method for preparing the conductive composite thin film according to claim 4, characterized in that, Step S2 includes: S21A. Mix high refractive index material and transparent elastic polymer material evenly to obtain composite colloid; S22A. The composite colloid is coated onto the surface of a transparent conductive network and cured to obtain a composite of the substrate and the conductive composite film. S23A. Cool the composite of the substrate and the conductive composite film to below the glass transition temperature of the transparent elastic polymer material, and separate the substrate from the conductive composite film to obtain the conductive composite film; or, Step S2 includes: S21B. Mix high refractive index material and transparent elastic polymer material evenly to obtain composite colloid; S22B: The transparent elastic polymer material and the composite colloid are sequentially coated onto the surface of the transparent conductive network, and after curing, a composite of the substrate and the conductive composite film is obtained. S23B. The composite of the substrate and the conductive composite film is cooled to below the glass transition temperature of the transparent elastic polymer material, and the substrate and the conductive composite film are separated to obtain the conductive composite film.

9. An application of the conductive composite thin film as described in any one of claims 1 to 3, characterized in that, The conductive composite film is used as the back electrode.

10. The application of the conductive composite film according to claim 9, characterized in that, The conductive composite film is used directly as the back electrode; or... The conductive composite film is composited with at least one of ITO and PEDOT:PSS films as a back electrode; and / or The conductive composite film is applied as the back electrode of an optoelectronic device using a dry bonding method.

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